Novel process for recovering colorforming coupler from used photographic color developer solutions



Drawing.

United States PatentO NOVEL PROCESS FOR RECOVERING COLOR- FORMING COUPLER FROM USED PHOTO- GRAPHIC COLOR DEVELOPER SOLUTIONS Courtenay D. Anselm, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey v Filed Feb. 28, 1962, Ser. No. 176,445 6 Claims. (Cl. 260-310) This invention relates to the recovery of color-forming coupler from used and/ or exhausted color developer solutions from photographic color development processes and more particularly to the recovery of acid color-forming couplers from the alkaline color developer solution by the addition of carbon dioxide.

Color developing solutions are used in the processing of exposed photographic elements for color photography in order to produce the dye images that form the color picture in the processed element. In the processing of three color substractive type photographic elements, the final picture is usually made by the formation of a cyan dye image, a yellow dye image and a magenta dye image in superposed relationship. The cyan dye image development is accomplished with an alkaline developer solution which contains a color developer and a cyanforming coupler which is usually a phenolic or naphtholic type coupler. Where exposed silver halide in the cyan image layer is developed to silver, color developer is oxidized to a compound that couples with the cyan-forming coupler present to form a nondiffusing dye image. The yellow dye image development is accomplished with an alkaline developer solution containing a color developer and a yellow dye-forming coupler. Similarly, the magenta dye image is developed with an alkaline developer containing a color developer and a magenta dye-forming coupler. Usually, acylacetamide type couplers are used in yellow dye-forming developers and a Z-pyrazolin-S- one or a coumarone type coupler is used in the magenta dye-forming developer. Each of these color-forming couplers have a reactive hydrogen on a methylene group that is adjacent to a keto group, or a reactive hydrogen atom on a methine group that is ortho to or para to a hydroxy group on an aromatic ring. 7

In addition to the color developer and color-forming coupler, ,the alkaline developer solution usually contains other constituents such as potassium bromide, sodium sulfite, sodium bisulfite, and other materials in order to give a developed image having the desired sensitometric characteristics (that is, relationship between exposure and resulting image density).

Commercial color processing is usually done on a continuous basis, in which a continuous flow of color film is processed through the various processing solutions including the color developers in a processing machine. Since the concentrations of the chemicals in the developer solutions (as well as other solutions) must be maintained within certain ranges to give good sensitometric results, it is common practice to replenish the various developers by a controlled flow of the appropriate replenisher solutions. In this way, the proper equilibria are maintained to give color development of optimum quality; Replenishment of the developer solution tanks in the processing machine results in displacement of used developer solution which is discarded.

Alternatively, when relatively small amounts of film are to be processed, a batch process may be used in which developer solutions are used until exhausted, then replaced with fresh developer for another batch of film.

In each type of processing, the exhausted or used developer solution still contains substantial concentrations of ICE the color-forming coupler. Because of the relatively high cost of the coupler compounds, it is advantageous to recover them for reuse in fresh developer solution.

It is known to recover these coupler compounds by the addition of concentrated mineral acid to precipitate the acid coupler which is then separated by filtration and purified for reuse. The handling of the mineral acids used in coupler recovery has presented many problems. These acids are dangerous to the operating personnel who must exert caution in handling them; and because of their highly corrosive nature, special acid resistant pumps and equipment must be used. In addition to these problems, it is necessary to carefully control the rate of acid addition in order to avoid local high concentrations of acid in the developer solution which causes too rapid a precipitation of coupler which adversely affects the quality of the recovered product. This control requires special equipment to meter acid flow to control pH, and close supervision by operating personnel.

It is, therefore, an object of my invention to provide an improved process for recovering color-forming couplers from used and/or exhausted color developer solutions.

Another object is to provide a coupler recovery process which does not require the use of an acid and, therefore, makes unnecessary the special acid handling equipment previously required. 7

Another object is to provide a novel coupler recovery process which uses carbon dioxide gas instead of a mineral acid to precipitate-the coupler.

Still another object is to provide a novel coupler recovery process which is safe to operating personnel, requires a minimum of control personnel and equipment, and in which it is impossible to get too rapid a rate of coupler precipitation.

Still further objects will be apparent from the following specification and claims.

These and other objects are accomplished according to my invention by dissolving carbon dioxide gas in the used or exhausted color developer solution until the soluble sodium (or potassium) salt of the coupler is converted to a precipitate consisting of the water-insoluble free acid form of the coupler. Then the precipitated coupler is separated from the solution by any suitable means, such as filtration or centrifuging, and the coupler product is then washed and dried.

Carbon dioxide gas is dissolved readily in the alkaline developer solution simply by bubbling the gas through the solution.

The used color developer solution from the processing machine tank is advantageously passed through a precipitation tank into which sufiicient carbon dioxide gas is introduced through a distribution system or sparger to precipitate all the coupler that will precipitate. This is ac- 'complished by adding carbon dioxide to lower the pH of the solution to the level at which the coupler salt is converted to the free acid coupler. The pH will depend upon the particular coupler recovered and can be determined readily by noting the pH below which no more coupler precipitates from a sample of the developer solution. The use of an excess of carbon dioxide is not detrimental to the recovered coupler quality. It is economically desirable to disperse the gas sufliciently so that almost all of it will be absorbed before it leaves the liquid. The solution in the precipitation tank is advantageously left at room temperature and atmospheric pressure throughout the operation; however, it is possible to operate at pressure above atmospheric if pressure vessels are available.

Any convenient source of carbon dioxide may be used for my coupler recovery process. It is particularly ad- 3 vantageous to use cylinders of compressed or liquified carbon dioxide. A simple pressure-reduction valve and a needle valve is all that is needed to control the flow of carbon dioxide gas from the pressurized cylinder of gas to the sparger in the precipitation tank.

The precipitated coupler is separated from the slurry formed in the precipitation tank by filtration or by centrifuging. The cake of coupler in the filter or centrifuge is washed with water and then dried before it is used to prepare fresh developer solution.

My coupler recovery process is used to advantage to recover the acid type color-forming couplers used in color developer solutions for processing color photographic materials.

Included among the cyan-dye forming couplers are the phenolic and the naphtholic type couplers such as the nitro-naphthol couplers of Vittum et al. U.S. 2,266,452, issued December 21, 1941; the naphtholic couplers of Porter et al. U.S. 2,295,009, issued September 8, 1942; the sub stituted naphthamide couplers of Salminen et al. U.S. 2,313,586, issued March 9, 1943; the phenolic couplers of Vittum et al. U.S. 2,338,676, issued January 4, 1944; the phenolic and naphtholic couplers containing sulfonamide groups of Schinzel U.S. 2,356,475, issued August 22, 1944; of Vittum et al. U.S. 2,362,598, issued November 14, 1944; the acylamino phenol couplers of Vittum et al. U.S. 2,369,929, issued February 20, 1945; the heterocyclic group substituted phenols and naphthols of Salminen et al. U.S. 2,976,146, issued March 21, 1961; the coupler 2 (o acetamido-fi-phenylethyl)-l-hydroxy naphthamide of Vittum et al. U.S. 3,002,836, issued October 3, 1961; etc.

Included among the yellow-dye forming couplers (and the developer solutions containing them) are those such as the acetoacetamides and cyanoacetamides of Mannes et al. U.S. 2,108,602, issued February 15, 1938; the acetoacetanilides of Mannes et al. U.S. 2,113,330, issued April 5, 1938; the diketone couplers of Vittum et al. U.S. 2,206,142, issued July 2, 1940; the sulfonamide substituted yellow couplers of Vittum et al. U.S. 2,271,238, issued January 27, 1942, and Vittum et al. U.S. 2,364,675, issued December 12, 1944; the sulfonic ester couplers of Porter et al. U.S. 2,289,805, issued July 14, 1942; the cyanoacetyl couplers of Allen et al. US. 2,313,498, issued March 9, 1943; the carboxylic acid amide couplers of Salminen et al. U.S. 2,359,332, issued October 3, 1944; the benzoyl acetanilide couplers of Weissberger et al. U.S. 2,407,210, issued September 3, 1946; the N-(benzoylacetyl)benzamide type couplers of Weissberger et al. U.S. 2,439,352, issued April 6, 1948.

Included among the magenta-dye forming couplers (and developer solutions containing them) are those such as the 3-substituted 2-pyrazolin5-ones of Porter et al. Re. 22,329 (of U.S. 2,311,082), reissued June 1, 1943; the iminopyrazolone couplers of Porter et al. US. 2,311,081, issued February 16, 1943; the 1,3-substituted 2-pyrazolin-5-one couplers of Porter et al. U.S. 2,343,703, issued March 7, 1944; the sulfonamide subsituted 2-pyrazolin-5-one couplers of Vittum et al. U.S. 2,353,205, issued July 11, 1944; the developer solution incorporated acylated amino 2-pyrazolin-5-one couplers of Porter et al. U.S. 2,369,489, issued February 13, 1945, the developer solution incorporated 1-cyanophenyl-3- acylamino-2- pyrazolin-S-one couplers of Weissberger et al. U.S. 2,511,231, issued June 13, 1950; etc.

Typical developer solutions containing these coupler materials are described in the references already given. These solutions contain a primary aromatic amino color developer, such as 2-amino-5-diethylamino toluene hydrochloride, N-ethyl-,B-methanesulfonamidoethyl-3- methyl-4-amino aniline sulfate and many others that are well known in the art. Other constituents that may be present in the developer solutions include sodium hydroxide, sodium sulfite, sodium sulfate, sodium carbonate, sodium thiocyanate, trisodium phosphate, sodium bromide, sodium iodide (or the corresponding potassium salts), etc. The following examples are used to further illustrate my invention but it is to be understood that my invention is not limited to these examples. 3

Ex mple 1 Used magenta developer solution containing the magenta dye-forming coupler 2-cyano acetyl coumarone was treated in a storage tank by bubbling carbon dioxide gas through a sparger at the bottom of the tank. Enough carbon dioxide gas was introduced to lower the pH of this solution to 7 to achieve full precipitation of the coupler. The coupler was separated, washed, and dried. The dried recovered coupler was used to make a fresh magenta developer solution.

Samples of color photographic film were image exposed. One set of the exposed samples were developed in a process which used this fresh magenta developer solution made from the recovered coupler and another set were developed in the same process using a fresh magenta developer solution which contained fresh nonrecovered coupler. The process using recovered magenta coupler produced color pictures of good quality, comparable to the quality produced by the nonrecovered coupler.

Example 2 Used cyan developer solution containing the cyanforming coupler 2 (o acetamido-[i-phenylethyl)-l-hydroxy naphthamide, from a color photographic processing machine, was passed through a precipitation tank into which enough carbon dioxide gas was introduced through a sparger to keep the pH at :03. The slurry, consisting of the precipitated acid form of the coupler in the developer solution, leaving the precipitation tank, was centrifuged. The recovered coupler after being washed with water and dried, was used to make fresh cyan developer solution. Image exposed color film processed with a process in which the recovered cyan coupler was used had the same good color quality as the other samples of the film that were processed with a process using fresh nonrecovered cyan coupler.

Example 3 Used magenta developer solution from the color processing machine was treated in another precipitation tank in which carbon dioxide gas was used as in Example 2 to precipitate (at a pH of 80:03) the magenta-dye forming coupler 1 (2,4,6 trichlorophenyl)-3-(4-nitroanilino)-2-pyrazolin-5-one. The recovered coupler was separated from the slurry by centrifuging, washed and dried. The dry recovered coupler was used to make a magenta developer solution. Samples of image exposed color film were processed through a process using the recovered magenta coupler and other identical exposed film was processed through a process using fresh (nonrecovered magenta coupler). The recovered magenta coupler was found to produce color pictures of good quality that was equivalent to the quality produced by fresh magenta coupler.

Example 4 r A used magenta developer solution from another color process was treated in a storage tank by bubbling carbon dioxide gas through a sparger at the bottom of the tank to precipitate the coupler 1-(2,4,6-trichlorophenyl)-3-(4- cyanoanilino)-2-pyrazolin-5-one. The precipitated coupler was separated, washed and dried as in Example 3. The recovered coupler was compared with fresh nonrecovered coupled as in Example 3 and was found to. give good quality in processed film.

carbon dioxide gas in the alkaline solution to convert the soluble alkali metal salt of the coupler to the water-insoluble free acid form of the coupler. This is done by introducing carbon dioxide gas into the developer solution through a sparger which may be in a precipitation tank or a storage tank. The process may be continuous or batch. The precipitated coupler is then separated 'by conventional means, washed with water, dried and reused. The process requires very little attention from operating personnel to produce recovered coupler of high quality. The process is controlled by a simple, inexpensive, maintenance free pressure-reducing valve and a needle valve. My process avoids the need for expensive acid resistant pumps and acid metering equipment required to handle the strong mineral acids needed in the recovery processes used previously, besides avoiding the expensive maintenance for this equipment, the close process control required and the dangers to operating personnel.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A process for recovering the color-forming coupler from the spent color-forming developer solution from photographic color development processes, said developer solution comprising Water, an alkali, a primary aromatic amino color developer, and a water-soluble salt of said coupler selected from the class consisting of the sodium salt and the potassium salt, said coupler being selected from the class consisting of a phenolic coupler, a naphtholic coupler, a 2-pyrazolin-5-one coupler, and an acetoacetanilide coupler comprising the steps of (1) dissolving suflicient carbon dioxide gas in the said developer solution to cause the precipitation of said coupler, and

(2) separating the precipitated coupler from the said developer solution.

2. A process for recovering a-benzoyl-o-methoxy acetanilide coupler from a developer solution comprising water, an alkali, a primary aromatic amino developing agent, and a water-soluble metal salt of said coupler 'selected from the class consisting of the sodium salt, and the potassium salt, said process comprising the steps of:

(1) dissolving sufficient carbon dioxide gas in the said developer solution to convert the water-soluble metal salt of said coupler to the water-insoluble a-benzoylo-methoxy acetanilide, and

(2) separating the said coupler.

3. A process for recovering l-hyd-roxy-N-(Z-acetamidophenylethyl)-2-naphthamide coupler from a developer solution comprising water, an alkali, a primary aromatic amino developing agent, and a water-soluble metal salt of said coupler selected from the class consisting of the sodium salt, and the potassium salt, said process comprising the steps of:

(l) dissolving sufiicient carbon dioxide gas in the said developer solution to convert the water-soluble metal salt of said coupler to the water-insoluble l-hydroxy- N-(Z-acetamidophenylethyl)-2-naphthamide, and

(2) separating the said coupler.

4. A process for recivering 1-(2,4,6-trichlorophenyl)- 3(4-nitroanilino)-2-pyrazolin-5-one coupler from a developer solution comprising Water, an alkali, a primary aromatic amino developing agent, and a water-soluble metal salt of said coupler selected firom the class consisting of the sodium salt, and the potassium salt, said process comprising the steps of:

(1) dissolving suflicient carbon dioxide gas in the said developer solution to convert the water-soluble metal salt of said coupler to the water-insoluble 1-(2,4,6- trichlorophenyl)-3-(4-nitroanilino) 2 pyrazolin-S- one, and

(2) separating the said coupler.

5. A process for recovering l-(2,4,6-trichlorophenyl)- 3-(4-cyanoanilino)-2-pyrazolin-5-one coupler from a developer solution comprising Water, an alkali, a primary aromatic amino developing agent, and a water-soluble metal salt of said coupler selected from the class consisting of the sodium salt, and the potassium salt, said process comprising the steps of (1) dissolving sufiicient carbon dioxide gas in the said developer solution to convert the water-soluble metal salt of said coupler to the water-insoluble 1-(2,4,6- trichlorophenyl) 3 (4-cyanoanilino)-2-pyrazolin-5- one, and

(2) separating the said coupler.

6. A process for recovering 2-cyano acetyl coumarone coupler from a developer solution comprising water, an alkali, a primary aromatic amino developing agent, and a water-soluble metal salt of said coupler selected from the class consisting of the sodium salt, and the potassium salt, said process comprising the steps of:

(l) dissolving sufiicient carbon dioxide gas in the said developer solution to convert the water-soluble metal salt of said coupler to the water-insoluble 2-cyano acetyl coumarone, and

(2) separating the said coupler.

References Cited by the Examiner FOREIGN PATENTS 9/60 Great Britain.

OTHER REFERENCES WALTER A. MODANCE, Primary Examiner.

NORMAN G. TORCHIN, Examiner. 

1. A PROCESS FOR RECOVERING THE COLOR-FORMING COUPLER FROM THE SPENT COLOR-FORMING DEVELOPER SOLUTION FROM PHOTOGRAPHIC COLOR DEVELOPMENT PROCESSES, SAID DEVELOPER SOLUTION COMPRISING WATER, AN ALKALI, A PRIMARY AROMATIC AMINO COLOR DEVELOPER, AND A WATER-SOLUBLE SALT OF SAID COUPLER SELECTED FROM THE CLASS CONSISTING OF THE SODIUM SALT AND THE POTASSIUM SALT, SAID COUPLER BEING SELECTED FROM THE CLASS CONSISTING OF A PHENOLIC COUPLER, A NAPHTHOLIC COUPLER, A 2-PYRAZOLIN-5-ONE COUPLER, AND AN ACETOACETANILIDE COUPLER COMPRISING THE STEPS OF: (1) DISSOLVING SUFFICIENT CARBON DIOXIDE GAS IN THE SAID DEVELOPER SOLUTION TO CAUSE THE PRECIPITATION OF SAID COUPLER, AND (2) SEPARATING THE PRECIPITATED COUPLER FROM THE SAID DEVELOPER SOLUTION. 